diff --git a/README.md b/README.md
index ff0e2028..53ac9e33 100644
--- a/README.md
+++ b/README.md
@@ -233,11 +233,11 @@ can achieve the same effect as the first example like this:
 
 There is a matching `weave detach` command:
 
-    host1# weave detach $C
+    host1# weave detach 10.0.1.1/24 $C
 
 You can detach a container from one subnet and re-attach it to another:
 
-    host1# weave detach $C
+    host1# weave detach 10.0.1.1/24 $C
     host1# weave attach 10.0.2.1/24 $C
 
 or attach a container to multiple subnets:
diff --git a/weaver/weave b/weaver/weave
index 589a2710..80d220c1 100755
--- a/weaver/weave
+++ b/weaver/weave
@@ -6,7 +6,7 @@ usage() {
     echo "weave launch <ipaddr>/<subnet> [-passwd <passwd>] <peer_host> ..."
     echo "weave run    <ipaddr>/<subnet> <docker run args> ..."
     echo "weave attach <ipaddr>/<subnet> <container_id>"
-    echo "weave detach <container_id>"
+    echo "weave detach <ipaddr>/<subnet> <container_id>"
     echo "weave expose <ipaddr>/<subnet>"
     echo "weave hide   <ipaddr>/<subnet>"
     echo "weave status"